NORTHEASTERN FOREST EXPERIMENT STATION 

Upper Darby , Pennsylvania 

No* 35 

August 1954 

Mice Cause Severe Damage 

To Virginia Pine Reproduction 

Heavy damage to a young Virginia pine stand was noticed recently on the Beltsville Experimental Forest in 

a Haryland. The injury was confined to pine trees that had 

come in on an abandoned field. This reproduction ranged from 

1 to 10 feet in height and had an average density of 19,000 

per acre. Andropogon was the predominant ground vegetation. 

The typical injury was a conspicuous wounding of the 

stem just above the ground line. The bark had been gnawed 

from portions of all the damaged trees. The wounds on individual trees were from 1 to 8 inches above the ground. On 

recently damaged trees, small beads of resin had formed on 

the exposed sapwood. Injuries several months old usually 

had a white resinous coating, and year-old injuries often 

had a black resinous rim. 

Experts from the Patuxent 

Research Refuge (u.s. Fish and 

Wildlife service) identified the 

damage as the work of meadow 

mice (~icrotus pennsylvanicus ) . These mice normally prefer such 

foods as grasses, sedges, and 

other tender foliage. Their 

girdling of trees usually occurs 

during the winter months. Although the mice store food supplies in their nests andtunnels, 

normal water supplies are often 

frozen in the winter: then tree 

sap may be the best available 

substitute. A mouse census made 

in May indicated that meadow 

mice had left the pine area. 

To measure the extent of 

the damage, three 1/100-acre 

stu y plots were established at P 

Virginia pine girdled 

by meadow mice. 
Table 1.--Meadow-mouse damage to a young stand of Virginia pine and pitch pine 

Inches Thousand Per- Per_ Per- Per- Per- Per- @ @osnt¢centl 

Species 

Virginia 0.1--0.4 i2.0 58 42 L!, 8 22 11, 

pine : 0.5+ 5.9 60 40 8 U 18 20 

Pitch 0.1--0.4 0.3 0 100 0 0 0 0 

pine : 0.5+ .6 20 80 5 5 5 5 

; 

*~easured 1 foot above ground line. 

random on the 1-acre damaged area. Observations were made 

on each plot of all trees that had attained a diameter of 

0.5 inch. Smaller trees (0.1 to 0.4 inch) were examined on 

1 milacre in each of the plots. The diameters were measured 

1 foot above the ground line to avoid interference with the 

girdle scar. Condensed results of the study are presented 

in table 1. 

~iametef 

A similar study of rodent injury in a young pine 

stand had been made on the Beltsville Experimental Forest in 

1945 by &rburg.* This was in an open-grown stand of mixed 

Virginia pine, pitch pine, and hardwoods. It showed that 

58 percent of the Virginia pine and 11 percent of the pitch 

pine had been injured by meadow mice. 

The results of the two studies are closely parallel. 

Both indicate that meadow mice decidedly prefer Virginia 

pine. No hardwoods were damaged on any of the plots. For 

Virginia pine, size of the tree made little difference (the 

largest tree injured was 2.2 inches in diameter). However, 

wounding of pitch pine was limited to trees between 0.5 and 

0.8 inch in diameter. 

Trees 

per 

In areas heavily stocked with Virginia pine seedlings 

mouse damage might be beneficial--by thinning the stand. 

However, such thinningis apt to be rather spotty. In poorly 

stocked areas, the girdling and subsequent mortality might 

be a serious matter. 

--THOMAS W. CHURCH, JR. 

Trees 

IRlured 

-x 

Marburg, F. W. Preferential girdling by mice in a 

mixed young stand of pitch and Virginia pine. (unpublished 

report. ) Northeast. Forest kpt. Sta. 1945. 

2 Agriculture-Forest Service-Upper Darby 

Portion of stem circumference wounded 

None 1/4 1/2 314 All